1. Field of the Invention
The present invention relates to an optical ribbon fiber, and more particularly to an optical ribbon fiber including a strength member.
2. Description of the Related Art
An optical fiber cable has a larger bandwidth, a smaller diameter, a lighter weight than those of a metal cable and a higher information rate. In addition, the optical fiber cable affords non-inductive broadband transmission with low transmission loss, and has been widely used instead of the metal fiber cable. Particularly due to its large bandwidth, a small diameter and a superior information rate while ensuring the broadband transmission at low transmission loss, optical fiber cable can simultaneously transmit various signals, such as a telephone sound and AV signals originating from different systems. For this reason, the optical cable fiber is widely used as a communication medium in the fields of public communication and cable community antenna television (cable CATV), and in factories, buildings, and laboratories. At present, the optical fiber cable forms the basis of an Integrated Services Digital Network (ISDN).
FIG. 1 shows an optical ribbon fiber 100 including optical fibers 110 aligned in series. Referring to FIG. 1, the optical ribbon fiber 100 has the optical fibers 110 aligned sideways in series and a ribbon coating layer 120 surrounding the optical fibers 110.
Each of the optical fibers 110 includes a core 111 formed at a center thereof and a clad 113 surrounding an outer surface of the core 111. A coating layer 112 is coated on an outer surface of the clad 113 in order to protect the core 111 and the clad 113. A coloring layer having any one of various possible colors can be coated on an outer surface of the coating layer 112 so as to readily distinguish the optical fibers 110 from each other. An optical signal longitudinally incident to the optical fiber 110 passes through the core 111 and is totally reflected at a boundary surface of the core 111 and the clad 113 due to a differential refractive index a the boundary.
The ribbon coating layer 120 includes an ultraviolet (UV) curing agent and is coated on outer surfaces of the optical fibers 110 aligned in series so as to bond the optical fibers 110 to each other.
FIG. 2 is a sectional view showing a conventional optical ribbon fiber 200 including a spacer 230. Referring to FIG. 2, the optical ribbon fiber 200 has a plurality of optical fibers 210 aligned sideways in series, a ribbon coating layer 220 coated on outer surfaces of the optical fibers 210, and at least one spacer 230 positioned between the optical fibers 210.
Each of the optical fibers 210 includes a core 211, a clad 212 and a coating layer 213 surrounding an outer surface of the clad 212.
The spacer 230 is interposed between the optical fibers 210 when the optical fibers 210 are aligned and has a size identical to a size of the optical fiber 210. The spacer 230 constantly maintains a space formed between the optical fibers 210 when aligning the optical fibers 210 and enhances the strength of the optical ribbon fiber 200. The ribbon coating layer 220 is coated on outer surfaces the spacer 230 and the optical fibers 210 aligned in series.
However, the above optical fiber is made of material having a weak tensile strength. Accordingly, making the optical ribbon fiber usable requires configuring it with a plurality of strength members and a plurality of elements capable of improving an environmental characteristic.
U.S. Pat. No. 6,421,487, which is issued to Curtis John Hutton, et. al., and entitled “Reinforced Buffered Fiber Optic Ribbon Cable”, discloses an optical ribbon fiber cable including an optical ribbon fiber formed with a reinforcement layer.
According to the Hutton's optical ribbon fiber cable, a reinforcement layer is coated on an outer surface of the optical ribbon fiber. In addition, the Hutton's optical ribbon fiber cable includes a central strength member and a plurality of auxiliary strength members for improving the tensile strength of the optical ribbon fiber cable. Furthermore, a plurality of wet-proof members are provided to improve the wet-proof characteristic of the optical ribbon fiber cable, thereby enhancing a physical characteristic of the optical ribbon fiber cable with respect to an external environment.
However, the Hutton's optical ribbon fiber cable requires complicated fabricating processes and enlarges an outer diameter of the optical ribbon fiber cable. That is, the Hutton's optical ribbon fiber cable uses a plurality of strength members and wet-proof members in order to enhance the tensile strength of the optical ribbon fiber cable and in order to improve the physical characteristic of the optical ribbon fiber cable with respect to the external environment. For this reason, the optical ribbon fiber cable is bulky in volume and costly to manufacture.